If you export a clip from Final Cut Pro to Soundtrack, delete the clip from the Soundtrack timeline, and then export it back again to Soundtrack, you may get the following error:
"File Error: The specified file is open and in use by this or another application."
To resolve this issue, quit Soundtrack so it can release the original clip you imported and then deleted. This issue can happen with Final Cut Pro HD 4.5 and Final Cut Pro 5.0, and either Soundtrack 1.x or Soundtrack Pro 1.0.